System and method for dismounted assured position, navigation and timing (DAPNT)

ABSTRACT

A process described herein may be used to determine a first asset&#39;s position in a GNSS-limited environment. The process includes transmitting a current position for each of at least three additional assets in wireless messages by wireless transmitters. The current position for each of the at least three additional assets is determined using previously received position data and one more additional measurement generated by instruments on board the additional assets. The transmitted messages are received at a device of the first asset and a processor on the device implements pre-programmed instructions to access the current position for each of the three additional assets and determine the first asset&#39;s position using the current position for each of the three additional assets.

BACKGROUND Field of the Embodiments

The present embodiments are generally directed to systems and methodsfor ascertaining reliable positional information in the field. Morespecifically, the present embodiments describe systems and methods forascertaining reliable positional information in the absence of (or asreal-time supplement to) traditional Global positioning system (“GPS”)data or more generally, Global Navigation Satellite System (GNSS).

Description of the Related Art

Due to the rise of GPS and other GNSS jamming, GPS denied areas or lowsignal areas (e.g., due to weather, bad communications links or enemyattack), there is an unmet need in the art for a method for determiningaccurate position information for assets while on the move. Accuratepositional information is crucial for both mounted and dismountedassets. Mounted Assured PNT (Position, Navigation and Timing) (A-PNT)Solution (MAPS) was created to give accurate position in jammed or DIL(Disconnected, Intermittent or Limited bandwidth) environments foron-vehicle applications. The MAPS system uses the last known real GPSlocation and then uses A-PNT (Assured PNT (Position, Navigation andTiming)) components including, for example, Chip Scale Atomic Clocks(CSAC), Inertial Navigation Units (INU), a GPS or DAGR (either internalor external to the device) and an Inertial Navigation System (INS), tomaintain position while on the move in GPS denied and DIL environments.When a GPS signal next becomes available, it is compared to the A-PNTlocation and the vehicle position is updated if needed. GPS drift is thecondition where the positional information that is obtained from the GPSsatellites moves over time. The lower the accuracy of the correctionsource, the more the positional information will move over time. Thehigher accuracy correction sources are still subject to GPS drift, butto a smaller amount. Exemplary MAPS systems include the VersaPNTprovided by Spectracom, an Orolia brand, and the DBH-670 and DBH-672Digital Beachhead products available from Curtiss-Wright.

In order to provide accurate PNT to dismounted warfighters, a differentsolution is needed. Dismounted PNT solutions are a primary focus ofgovernment-funded research. In 2016, the Army posted a “Request forInformation (RFI) for: Assured Positioning, Navigation, and Timing”Solicitation Number: W56KGY-16-R-APNT (hereafter “RFI Solicitation”)which solicited industry feedback on the requirements and proposedacquisition strategy for the Assured Positioning, Navigation, and Timing(A-PNT) program. The A-PNT family of solutions includes dismountedsolutions, e.g., PNT receiver, with non-GPS augmentation, whichdistributes PNT to systems on dismounted soldiers as described in theBackground of the RFI Solicitation. And in November of 2017 the Armyposted a Broad Area Announcement (BAA) for “Positioning, Navigation, andTiming” Solicitation Number: W56KGU-18-R-PN22 (hereafter “BAASolicitation”) that included numerous research interest topics relevantto providing PNT to dismounted soldiers. Both the RFI and BAASolicitations are incorporated herein by reference.

Prior art solutions and proposed solutions include ground basedpseudolites (short for pseudo-satellites) which are towers withrepeaters that need to be moved with ground troops and/or providing thedismounted warfighter with additional hardware (e.g., GPS, INU, INS,CSAC and a processing unit) for the Warfighter to wear. The formerrequires time to move and set up the towers and is not conducive for theon-the-move force. The latter adds more weight to the warfighter andcreates the need for smaller, ruggedized A-PNT devices.

Current processor-based node-to-node communication anddistance-determination processes are susceptible to processing delays orlatency for prioritization and contention throughput. And these delaysincrease with number of nodes. Accordingly, there is an unmet need inthe art to enable, protect and unencumber the dismounted warfighter byadding A-PNT capability without the additional weight of added hardware.

SUMMARY OF THE EMBODIMENTS

In a first exemplary embodiment, a process for determining a firstasset's position in a GNSS-limited environment, the process comprising:transmitting a current position for each of at least three additionalassets in wireless messages by wireless transmitters, wherein thecurrent position for each of the at least three additional assets isdetermined at each of the three additional assets using previouslyreceived position data and one more additional measurements generated byinstruments on board the mounted assets; and receiving the wirelessmessages at a receiving device located at the first asset from each ofthe at least three additional assets, wherein the receiving deviceimplements pre-programmed instructions on a processor therein to accessthe current position for each of the three additional assets anddetermine the first asset's position using the current position for eachof the three additional assets.

In a second exemplary embodiment, a device for determining a location ofthe device in a GNSS-limited environment comprising: a receiving devicefor receiving one or more wireless messages from one or more nodeswithin a predetermined communications range, the receiving deviceincluding: at least one antenna for receiving the one or more wirelessmessages; a processor pre-programmed with instructions for: accessingcurrent position information from a payload of the messages for each ofthe one or more transmitting assets, and calculating the location of thedevice using the current position information for at least three of theone or more assets; and a display for displaying the location of thedevice in a visual format.

In a third exemplary embodiment, a process for determining a firstasset's position in a GNSS-limited environment, the process comprising:receiving one or more wireless messages by at least one antenna in adevice located at the first asset; processing each of the one or morewireless messages by a processor on the device using pre-programmedinstructions to: receive one or more wireless messages transmitted fromone or more transmitting assets within a predetermined Wi-Fi range ofthe device located at the first asset, access current positioninformation from a payload of the wireless messages for each of the oneor more transmitting assets, and calculate the first asset's positionusing the current position information for at least three of the one ormore transmitting assets; and displaying by a display of the device thefirst asset's position in a visual format.

In a fourth exemplary embodiment, a system for determining a firstasset's position in a GNSS-limited environment, the system comprising:at least three additional assets, wherein at least one of the threeadditional assets includes at least a primary mounted asset navigationsystem, wherein, using previously-obtained GNSS position data, theprimary mounted asset navigation system generates a current position forthe mounted the at least one additional asset when the at least oneadditional mounted asset is in a GNSS-limited environment; the at leastthree mounted additional assets further including a wireless transmitterfor transmitting the current position for each of the three mountedadditional assets to the first asset using an encrypted wirelessmessage; and a receiving device located at the first asset for receivingthe encrypted wireless messages from each of the at least three mountedadditional assets, the receiving device including a processorpre-programmed with instructions for decrypting each of the encryptedmessages, accessing the current position for each of the threeadditional assets and determining the first asset's position using thecurrent position for each of the three additional assets.

BRIEF DESCRIPTION OF THE FIGURES

The following figures are intended to represent exemplary embodimentsand should be considered in combination with the detailed descriptionbelow.

FIGS. 1a and 1b are schematics illustrating how distance to nodes isinsufficient to determine warfighter location without node positiondata;

FIGS. 2a, 2b, and 2c are schematics illustrating how at least three setsof distance and position data are required to determined warfighterlocation;

FIG. 3 is a schematic showing an exemplary field situation with multiplenodes and assets; and

FIG. 4 is a flowchart of an exemplary process for determining dismountedasset location in accordance with an embodiment described herein.

DETAILED DESCRIPTION

As used herein the term asset refers broadly to physical systems(vehicles, vessels, aircraft, weapons, both manned and unmanned) orpersonnel (e.g., warfighters). The modified term mounted asset isgenerally recognized in the art as referring to an asset which can bemounted by personnel such as vehicles and other physical systems.Similarly, the term dismounted asset is generally recognized in the artas referring to personnel, e.g., warfighters, who are have dismountedfrom a vehicle or other physical system. In the descriptions ofembodiments herein, mounted assets are considered to have A-PNTcapabilities, while dismounted assets do not. Further, though theembodiments refer to dismounted assets as being synonymous withwarfighters, the disclosure is not so limited. A dismounted asset couldbe a drone or other unmanned ground or aerial vehicle (UAV, UGV).

As described further herein, the present embodiments are directed to asolution that extends the A-PNT capability from a ground vehicle (orother asset) through an encrypted Wi-Fi device on the vehicle and usesmethods at the receiving dismounted asset (e.g., warfighter) todetermine distances from the transmitting source(s) and thus the currentlocation of the receiving asset. Using standard trilateration methods,the dismounted warfighter can determine their exact grid coordinateposition. This allows dismounted warfighters to maintain communicationsand have grid coordinate map location available in a secure method. Asthe warfighter dismounts from the vehicle, they are able to ascertainaccurate PNT information from a mesh network of other A-PNT enabledvehicles thus extending the area of PNT without having to set up, breakdown, move and reset pseudolites. Certain systems and embodiments avoidthe need for additional warfighter-borne hardware. The warfighterhardware that may be used in certain embodiments is a warfighter-borneand Wi-Fi enabled smartphone, tablet, watch or the like with aprogrammed application for performing the functions described herein.Knowing in real time the locations of dismounted warfighters, as well asother vehicles, reduces fratricide and facilitates mission success.Although the term “warfighter” is used herein in connection with certainexamples, the described systems and methods may be used to determine alocation of any person or object.

The present embodiments are directed to a dismounted A-PNT (DAPNT)system and methodology that provides the dismounted warfighter with thecapability to know their position in GPS denied or DIL environmentswithout excessive equipment and cost. As discussed herein, DAPNT putsthe burden of processing and geo-location on the A-PNT enabled vehiclesor other locations, via MAPS or other systems, rather than on hardwareand software carried by the dismounted warfighter. DAPNT can use knownover-the-air (OTA) distance measurement calculations to determinedistance to the timing signal sources, but more than known distance isneeded. For example, as shown in FIGS. 1a and 1b , both figures show thevehicles at 1000 m, 800 m and 500 m from the warfighter. Both arecorrect given the distances to the vehicles, but this information alonedoes not provide assured PNT. On the other hand, if the startingpositions of the three vehicles are known in addition to the distancebetween the warfighter and each of the three vehicles, the location ofthe warfighter can be determined. However, these calculations becomemore complicated if the vehicles are in motion. In traditional GPS orcell tower configurations, the positions of the sources (e.g., vehicles)are known, and a simple calculation can be made to determine thewarfighter's position relative to the known sources and theirgeo-coordinates.

In one embodiment, the DAPNT system and method utilizes MAPStechnologies and VICTORY (or other common language messaging format)messaging to send a position message to the warfighter that contains thegeolocation of the vehicle. The vehicle-borne MAPS unit maintains anaccurate map position for the vehicle, even in GPS disruptedenvironments. VICTORY or Vehicular Integration of C4ISR/EWInteroperability is a Government created optimization architecture whichallows the sharing of services to be used by many consuming systems onthe vehicle. For instance, a single GPS can be utilized by many systemsthat require GPS so that these systems do not need to bring their ownGPS, thus reducing the Size, Weight and Power (“SWaP”) for the platform.

In one embodiment, the mounted vehicle contains an Assured-Position,Navigation & Timing (A-PNT) device (MAPS) that is VICTORY enabled. TheA-PNT device is preferably protected inside an armored vehicle. Thevehicle's power pack delivers sufficient energy thereto and can enablelong-range communications (in one example, Wi-Fi) to the dismountedwarfighter. Examples of various MAPS-like systems that may be consideredby one skilled in the art for use with the present embodiments aredescribed in U.S. Pat. Nos. 6,671,622, 7,409,290, U.S. PatentPublication 2015/0276783, and Chinese Patent No. 104931993, the contentsof which are incorporated herein by reference in their entireties. Inaddition, or alternatively, the VersaPNT provided by Spectracom, anOrolia brand, and the DBH-670 and DBH-672 Digital Beachhead productsavailable from Curtiss-Wright may be used in accordance with thedisclosed embodiments.

Various types of communications technologies may be used in connectionwith the disclosed embodiments. By way of example only, commerciallyavailable Wi-Fi ranges are in the 800-1000 m range (e.g., telephonicsIAIU NSA type 1 encrypted). In one example, a mile long range (1600 m)antenna may be used. One skilled in the art will understand that with anincrease in available power, the Wi-Fi communications range may beincreased. In operation, the vehicle's INS takes the A-PNT MAPS vehicleposition data and checks it against the GPS/DAGR vehicle position data(when available) to make any corrections. In GPS denied (jammed, low orno GPS signal) areas as well as DIL (Disconnected, Intermittent orLimited bandwidth) environments, the A-PNT MAPS vehicle position data isthe primary position source with the GPS/DAGR as the secondary source.The INS is set to intervals that can be almost real time. In a GPS DILenvironment, whenever GPS is detected by the vehicle's INS, it iscompared to the most recent A-PNT MAPS vehicle position data, but theA-PNT MAPS vehicle position data is the primary position device in theGPS DIL environment.

The A-PNT MAPS vehicle position data is sent to the dismountedwarfighter via a secure OTA (Over-The-Air) transport (radio ornon-radio) in a VICTORY message, where it is received and read by aDAPNT software application (App) running on the warfighter's receivingdevice to ascertain the exact location(s) of the vehicle(s) and thedistance to those vehicle(s). The DAPNT App is also equipped withprogramming and hardware (as the case may be) for determining distancebetween the warfighter and the vehicle using one or more knownmethodologies for determining distances between wireless nodes. Forexample, using time-of-arrival (TOA) calculations, the time differencebetween sending a data packet from a first to a second node andreceiving the immediate acknowledgement from the second node wouldprovide a distance measurement. This process is described in A. Gunther,et al, Measuring Round Trip Times to Determine the Distance between WLANNodes, In Proc. of Networking 2005, Waterloo, Canada, May 2005, which isincorporated herein by reference. In one embodiment, the Warfighter'sprocessor, e.g., smart device with DAPNT App, receives a vehicleposition message with a time stamp indicating time sent from the vehicleand then compares with the time the message was received at the DAPNTApp to determine distance to the vehicle.

One skilled in the art recognizes that alternative methodologies fordetermining distance may be used, such as Received Signal StrengthIndication (RSSI). The RSSI process is described in F. Viani, et al.,Object Tracking Through RSSI Measurements in Wireless Sensor Networks,Technical Report # DISI-11-005, University of Trento Dipartimento DiIngegneria E Scienza Dell'informazione, May 2008 which is incorporatedherein by reference. And a third exemplary method for measuring distancebetween two nodes could also be implemented, wherein pulse repeaters atthe vehicles and the warfighter endlessly repeat a pulse generating ameasurable frequency that varies inversely with the distance to bemeasured as described by Sergio Elias Hernandez et al., Distance andCable Length Measurement System, MDPI Sensor Journal, October 2009,incorporated herein by reference.

If distance measurements from the dismounted warfighter to three or moreknown-location nodes are available, then a location of the dismountedwarfighter could be determined by the DAPNT App using trilaterationtechniques. As the warfighter moves in and out of the range of variousA-PNT-enabled MAPS vehicles (or other nodes), the mesh network of nodesmaintains connectivity and constantly updates the DAPNT App to give thewarfighter their most current location. When GPS (GNSS) is restored, theDAPNT app checks the GPS location from the dismounted warfighter's GPSdevice against the current DAPNT App generated location as determinedusing the received A-PNT MAPS vehicle (or node) position data andsynchronizes the data accordingly to update the warfighter's positionwith the most accurate data.

Utilizing the A-PNT MAPS vehicle (or node) position data delivered viaVICTORY messaging as the warfighter's DAPNT position source alleviatesthe need for the warfighter's navigation system to switch GPS messagesources between DAPNT and GPS as they can work concurrently. This allowsthe dismounted warfighter's DAPNT App to check both GPS and VICTORYposition messages simultaneously. With the warfighter's DAPNT as theprimary source for position (utilizing VICTORY messages and distancefrom vehicles) and actual GPS as a secondary source, the DAPNT App cancontinually check the DAPNT location against the actual GPS locationwhen and if it is available.

The accurate grid coordinate position of the dismounted Warfighter maybe determined using trilateration, which is the method employed todayfor locating one's position via GPS. When GPS data (or other GNSS) isavailable, GPS receivers use trilateration (a more complex version oftriangulation) to determine its position on the surface of the earth bytiming signals from a minimum of three GPS satellites. The GPSdetermines absolute or relative locations of points by measurement ofdistances, using the geometry of circles, spheres or triangles. As thename suggests it uses at least three time sources to find the positionof an object. For GPS, the time sources are the 31 geodesic satellitesin orbit around the globe that provide GPS information. For cell phones,it is the cell phone towers. The process is the same regardless of theorigin of the signal.

Referring to FIG. 2a , with a single timing signal, the warfighter canbe anywhere on the perimeter of the circle formed by the known distancefrom the source. Accordingly, this single datapoint is not sufficient todetermine warfighter location. Referring to FIG. 2b , using two timingsignals with known distances we see that the circles overlap, and theposition may be one of two places on the converging circles. Again, theinformation in FIG. 2b is not sufficient for an accurate positiondetermination. Finally, adding a third timing signal, we are able tofind the single spot where all three circles converge to form the pointwhere we find the location of the dismounted warfighter (FIG. 2c ). Andaccuracy greatly improves as the number of received signals increasesbeyond the required three. More sampling iterations results in a higherdegree of accuracy, which becomes important for On-The-Move (OTM)situations, i.e., situations in which the warfighter is physicallymoving.

In one embodiment, the VICTORY message(s) containing each node's A-PNTvehicle position information are contained in the payload of a secureOTA data packet utilizing, e.g., the IEEE 802.11ac wireless networkingstandard in the 802.11 family developed in the IEEE StandardsAssociation, which provides high-throughput wireless local area networks(WLANs) on the 5 GHz band. The standard was developed from 2008 (PARapproved Sep. 26, 2008) through 2013 and published in December 2013 andis incorporated herein by reference. The specification has multi-stationthroughput of at least 1 gigabit per second and single-link throughputof at least 500 megabits per second (500 Mbit/s). This is accomplishedby extending the air-interface concepts embraced by 802.11n: wider RFbandwidth (up to 160 MHz), more Multi-user, Multiple-Input,Multiple-Output (MU-MIMO) spatial streams, downlink multi-user MIMO, andhigh-density modulation (up to 256-QAM). Cisco's Technical White Paperentitled “802.11ac: The Fifth Generation of Wi-Fi” is incorporatedherein by referenced for its teachings.

MU-MIMO technology allows a router to communicate with multiple devicessimultaneously. This decreases the time each device has to wait for asignal and dramatically speeds up the network. MU-MIMO allows one802.11ac device to transmit individual data streams to multipledifferent clients at the same time. This removes multiple nodes on thesame data streams. The 802.11ac standard is a chip based solution thatremoves the latency that an operating system based solution may induce.Under older 802.11 protocols (e.g., 802.11b, g and n), users are servedon a first come, first serve basis. MU-MIMO was created to supportenvironments where multiple users are trying to access the wirelessnetwork at the same time. When multiple users begin accessing the routerat or near the same time, congestion can be introduced as the routerservices the first user's request while the second (and third, fourth,etc.) wait. While these times can be miniscule, it can add up with moredevices (smartphones, tablets, computers, etc.) and users asking forresources. MU-MIMO helps this by allowing for multiple users to accessrouter functions without the congestion. Compared to single user MIMOand earlier wi-fi protocols, MU-MIMO has more spatial streams, i.e., theamount of signals that can be transmitted simultaneously from one deviceusing different antennas; larger bandwidth channels, i.e., the rate atwhich data passes between two devices; capacity, i.e., more bandwidthavailable and better distribution mean—instead of 30 to 40 clients(nodes) the system can support 80 to 100; range, i.e., placed at thesame distance 802.11ac devices will have increased data or connectionrates; and speed, i.e., increased bandwidth capabilities starting at upto three times more. In the present embodiments, the A-PNT MAPS hardwaremay be equipped with an 802.11ac device operable in a MU-MIMOconfiguration. This facilitates transmission of A-PNT MAPS vehicle (ornode) position data via VICTORY messaging from a single vehicle tomultiple warfighters simultaneously.

Referring to FIG. 3, an exemplary field situation is shown, wherein GPSsignals are not available to on-the-ground assets, including dismountedwarfighters 5 a and 5 b, tanks 10 a, 10 b, 10 c, ground vehicles 15 a,15 b or tower 20. In the absence of available GPS data, tanks 10 a, 10b, 10 c, and ground vehicles 15 a, 15 b are equipped with A-PNT MAPStechnology and tower 20 has a fixed, i.e., known position. These assetsform a mesh network. Dismounted warfighters 5 a and 5 b having at leastone smart appliance (e.g., phone, tablet, watch) equipped with a DAPNTApp and being in communicative Wi-Fi proximity to at least threetransmitting assets within the mesh network, can ascertain necessarydata to establish warfighter position. Further, all transmitting assetswithin Wi-Fi proximity of one another can exchange data relevant to PNTin order to stay as up-to-date as possible. The numerous point-to-pointconnections across the asset mesh are shown as A-L. In accordance withthe process described herein, dismounted warfighter 5 a can ascertainlocation using at least mesh connections A, B, and C. And dismountedwarfighter 5 b can ascertain location using at least mesh connections F,G, and H. It should be appreciated by those skilled in the relevant artthat the number, location and types of assets represented in FIG. 3 areintended to be merely exemplary. Further, although FIG. 3 suggests thatall of the assets in the mesh are GPS-denied, this may not be the case.Some assets in the mesh might never be GPS-denied or may intermittentlyreceive GPS data while the dismounted warfighter remains constantlyGPS-denied.

FIG. 4 provides an exemplary process flow in accordance with oneembodiment. With reference to dismounted Warfighter 5 a from FIG. 3,dismounted Warfighter 5 a as well as all other grounded assets are in aGPS-denied environment. Assets 10 a, 10 b are equipped with A-PNT MAPStechnology and are able to ascertain position information withoutcurrent GPS data, while transceiver tower 20 has a known position.Accordingly, assets 10 a, 10 b and 20 within Wi-Fi range of dismountedWarfighter 5 a transmit VICTORY messages in encoded data packets usinge.g., 802.11ac format, which are received by dismounted Warfighter 5 a(S10). The dismounted Warfighter's DAPNT App decodes received datapackets to obtain VICTORY message data, including node positioncoordinates for the transmitting asset S15. Simultaneously or shortlythereafter, the DAPNT App determines distance to the transmitting assetuse one or more of the methods described herein S20. Once the DAPNT Appdetermines that there are at least three available (position, distance)data sets S25, the DAPNT App is able to use trilateration to determinethe receiving dismounted warfighter's current position coordinates S30.When/if GPS data becomes available to the Warfighter, GPS-calculatedposition coordinates are compared to the A-PNT MAPS generated Warfighterposition coordinates S35 to confirm and/or update as is appropriate S40.Note that the position coordinates for the transceiver tower 20 could bepreviously known and stored in a database associated with the DAPNT App(or readily accessible thereby) or the transceiver tower 20 could bealso be A-PNT enabled movable asset which calculates and transmits itsposition coordinates in VICTORY messages as discussed above. Further,one skilled in the art recognizes that as GPS data becomes available toassets within Wi-Fi range of the dismounted Warfighter 5 a, the positioncoordinates in the VICTORY messages transmitted by those assets will beupdated accordingly.

Similarly, it should be understood that the functions of the DAPNT Appcan be selectively set to operate in different modes in accordance withthe Warfighter's location-determination requirements, as well asremaining power considerations. That is, the DAPNT App could be set tocontinuously update a Warfighter's position in accordance with theprocesses described herein and either provide continual display thereofon a display screen of the Warfighter's smart appliance (e.g., phone,tablet, watch). Alternatively, the DAPNT App could be set to wait for arequest from the Warfighter before receiving wireless messages andcalculating and displaying the Warfighter's position. It will also beappreciated that the DAPNT App could include map overlay capability,wherein the calculated Warfighter position is displayed on a map so asto orient the Warfighter with respect to underlying terrain, as well asthe locations of other assets (nodes).

One skilled in the art will appreciate the variations and additions tothe present embodiments which are well within the scope thereof,regardless of explicit inclusion in this document. For example, whilesome embodiments describe a Wi-Fi communications network fortransmission between assets under the 802.11 standard, other protocolsand standards are contemplated. For example, Dedicated Short-RangeCommunication (DSRC) enables vehicular communication using periodicbroadcast messages. DSRC is a two-way short-to-medium-range wirelesscommunications capability that permits very high data transmissioncritical in communications-based active safety applications. In Reportand Order FCC-03-324, the Federal Communications Commission (FCC)allocated 75 MHz of spectrum in the 5.9 GHz band for use by IntelligentTransportations Systems (ITS) vehicle safety and mobility applications.Currently the subject of research in the area of vehicular collisionavoidance, the DSRC could be of use as the primary or possibly asupplemental communications standard with the present embodiments.

The invention claimed is:
 1. A process for determining a first asset'sposition in a GNSS-limited environment, the process comprising:transmitting a current position for each of at least three additionalassets in wireless messages by wireless transmitters, wherein thecurrent position for each of the at least three additional assets isdetermined at each of the three additional assets using previouslyreceived position data and one more additional measurement generated byinstruments on board the mounted assets; and receiving the wirelessmessages at a receiving device located at the first asset from each ofthe at least three additional assets, wherein the receiving deviceimplements pre-programmed instructions on a processor therein to accessthe current position for each of the three additional assets anddetermine the first asset's position using the current position for eachof the three additional assets.
 2. The process according to claim 1,wherein the wireless messages are encrypted and further wherein thereceiving device implements pre-programmed instructions on the processorto decrypt each of the encrypted messages.
 3. The process according toclaim 1, wherein the previously received position data is GNSS data. 4.The process according to claim 1, further comprising: receiving GNSSlocation data at a GNSS-receiver associated with the receiving device atthe first asset and comparing the GNSS location data to the determinedfirst asset's position and updating current first asset position inaccordance with the received GNSS location data.
 5. The processaccording to claim 1, wherein at least one of the three additionalassets is stationary.
 6. The process according to claim 2, wherein theencrypted wireless messages are time stamped with the time oftransmission by each of the wireless transmitters.
 7. The processaccording to claim 1, wherein the processor determines the first asset'sposition using a trilateration process.
 8. The process according toclaim 2, wherein the encrypted wireless messages are transmitted andreceived across a distance of up to 1000 meters.
 9. The processaccording to claim 2, wherein the encrypted wireless messages aretransmitted in accordance with an 802.11ac standard.
 10. A device fordetermining a location of the device in a GNSS-limited environmentcomprising: a receiving device for receiving one or more wirelessmessages from one or more nodes within a predetermined communicationsrange, the receiving device including: at least one antenna forreceiving the one or more wireless messages; a processor pre-programmedwith instructions for: accessing current position information from apayload of the messages for each of the one or more transmitting assets,and calculating the location of the device using the current positioninformation for at least three of the one or more assets; and a displayfor displaying the location of the device in a visual format.
 11. Thedevice according to claim 10, wherein the one or more wireless messagesare encrypted and further wherein the receiving device implementspre-programmed instructions on the processor to decrypt each of theencrypted messages.
 12. The device according to claim 10, wherein thepredetermined communications range is Wi-Fi.
 13. The device of claim 10,wherein the receiving device further includes a GNSS receiver forreceiving GNSS signals when the GNSS signals are available.
 14. Thedevice of claim 11, wherein the one or more encrypted wireless messagesare formatted in accordance with an 802.11ac standard.
 15. The device ofclaim 11, wherein the one or more encrypted wireless messages includes atime stamp indicating time of transmission.
 16. The device of claim 12,wherein the predetermined Wi-Fi range is up to 1000 meters.
 17. Aprocess for determining a first asset's position in a GNSS-limitedenvironment, the process comprising: receiving one or more wirelessmessages by at least one antenna in a device located at the first asset;processing each of the one or more wireless messages by a processor onthe device using pre-programmed instructions to: receive one or morewireless messages transmitted from one or more transmitting assetswithin a predetermined Wi-Fi range of the device located at the firstasset, access current position information from a payload of thewireless messages for each of the one or more transmitting assets, andcalculate the first asset's position using the current positioninformation for at least three of the one or more transmitting assets;and displaying by a display of the device the first asset's position ina visual format.
 18. The process according to claim 17, wherein the oneor more wireless messages are encrypted and further wherein the deviceimplements pre-programmed instructions on the processor to decrypt eachof the received one or more encrypted wireless messages.
 19. The processaccording to claim 17, further comprising: receiving GNSS location dataat a GNSS-receiver in the device at the first asset and comparing theGNSS location data to the calculated first asset's position and updatingthe display of the device to display a current position of the firstasset in accordance with the received GNSS location data.
 20. Theprocess according to claim 17, wherein at least one of the at leastthree transmitting assets is stationary.
 21. The process according toclaim 18, wherein the one or more encrypted wireless messages are timestamped with the time of transmission by each of the one or moretransmitting assets.
 22. The process according to claim 17, wherein theprocessor determines the first asset's position using a trilaterationprocess.
 23. The process according to claim 18, wherein the encryptedwireless messages are transmitted and received across a distance of upto 1000 meters.
 24. The process according to claim 18, wherein theencrypted wireless messages are transmitted in accordance with an802.11ac standard.
 25. A system for determining a first asset's positionin a GNSS-limited environment, the system comprising: at least threeadditional assets, wherein at least one of the three additional assetsincludes at least a primary mounted asset navigation system, wherein,using previously-obtained GNSS position data, the primary mounted assetnavigation system generates a current position for the at least oneadditional asset when the at least one additional asset is in aGNSS-limited environment; the at least three additional assets furtherincluding a wireless transmitter for transmitting the current positionfor each of the three additional assets to the first asset using anencrypted wireless message; and a receiving device located at the firstasset for receiving the encrypted wireless messages from each of the atleast three additional assets, the receiving device including aprocessor pre-programmed with instructions for decrypting each of theencrypted messages, accessing the current position for each of the threeadditional assets and determining the first asset's position using thecurrent position for each of the three additional assets.